Some other suggestions :
- In endless, why not having rooms (levels) with a specific field of view (such as in the other dungeons : different activation range, dark, minefield) ? It would be activated when breaking the door, and until next door is broken
- Endless is described as a meditative experience. I don't find it very meditative. But what if there were subdungeons (have you played desktop dungeons ?), as places to relax a bit. ie you are teleported in a small room. Maybe a place devoid of ennemies (or some powerups), and something interesting, such as a statue of the object which killed you the most. Counting player kills is not that trivial in endless, however a rule could be that in checkmate every item threatening the player gets a kill. Also, when starting an undo streak, every item threatening the player on first undo gets a kill. The fun part would be even friendly items might threat you (a bullet destroying door and erasing you door. Or a friendly bomb). If you die of starvation, you are the treat. I feel that such rooms with this statue would be a fun, interesting, and relaxed places for meditation